SESSIONTIMEZONE FAQS

 1. What is SESSIONTIMEZONE in Oracle?

• SESSIONTIMEZONE is a function in Oracle that returns the time zone offset of the current session in the format of an interval (e.g., +02:00 or -08:00). This reflects the time zone that is set for the user's session and may differ from the database's time zone (DBTIMEZONE).

2. How does SESSIONTIMEZONE differ from DBTIMEZONE?

• DBTIMEZONE reflects the time zone of the database server, and it remains the same for all sessions connected to that database.
• SESSIONTIMEZONE reflects the time zone of the current session. This can vary across sessions, allowing users to have different time zones for each session.

3. How do I retrieve the session time zone in Oracle?

• You can retrieve the time zone of the current session using the following query:

SELECT SESSIONTIMEZONE FROM dual;

4. Can I change the session time zone?

• Yes, you can change the session's time zone using the following command:

·        ALTER SESSION SET TIME_ZONE = 'desired_time_zone';

For example:

ALTER SESSION SET TIME_ZONE = 'America/New_York';

5. How do I set the session time zone to a specific region or offset?

• You can set the session time zone to a specific region (e.g., 'America/Los_Angeles') or an offset (e.g., '-08:00') using the ALTER SESSION command:

ALTER SESSION SET TIME_ZONE = 'America/Los_Angeles';

6. What happens if I don't set the session time zone?

• If you don't explicitly set the session time zone, the session will default to the database’s time zone (as defined by DBTIMEZONE).

7. Does SESSIONTIMEZONE handle Daylight Saving Time (DST)?

• Yes, SESSIONTIMEZONE automatically adjusts for Daylight Saving Time (DST). If the session’s time zone includes DST changes (like America/New_York), the time zone offset will adjust accordingly when DST starts or ends.

8. How do I adjust the SYSTIMESTAMP or LOCALTIMESTAMP to my session time zone?

• You can adjust the SYSTIMESTAMP or LOCALTIMESTAMP to the current session’s time zone using the AT TIME ZONE clause:

SELECT SYSTIMESTAMP AT TIME ZONE SESSIONTIMEZONE FROM dual;

SELECT LOCALTIMESTAMP AT TIME ZONE SESSIONTIMEZONE FROM dual;

9. How do I compare SESSIONTIMEZONE with DBTIMEZONE?

• You can compare the session time zone with the database's time zone by querying both SESSIONTIMEZONE and DBTIMEZONE:

SELECT SESSIONTIMEZONE, DBTIMEZONE FROM dual;

10. Can SESSIONTIMEZONE be used with TIMESTAMP WITH TIME ZONE?

• Yes, SESSIONTIMEZONE can be used with TIMESTAMP WITH TIME ZONE to convert timestamps to the current session’s time zone. For example:

SELECT CAST(SYSTIMESTAMP AS TIMESTAMP WITH TIME ZONE) AT TIME ZONE SESSIONTIMEZONE FROM dual;

11. How do I adjust timestamps for the session’s time zone?

• To adjust a timestamp to the session's time zone, you can use AT TIME ZONE SESSIONTIMEZONE. For example:

SELECT some_timestamp_column AT TIME ZONE SESSIONTIMEZONE FROM some_table;

12. Can SESSIONTIMEZONE be used in date and time arithmetic?

• Yes, you can perform date and time arithmetic in the context of the session's time zone. For example:

SELECT LOCALTIMESTAMP + INTERVAL '1' HOUR AT TIME ZONE SESSIONTIMEZONE FROM dual;

13. What happens when I change the session time zone?

• When you change the session time zone, the session’s SESSIONTIMEZONE will reflect the new time zone offset, and any date/time values retrieved or stored will be adjusted according to this new time zone.

14. How do I check if SESSIONTIMEZONE is different from DBTIMEZONE?

• You can check if SESSIONTIMEZONE differs from DBTIMEZONE by comparing both values:

SELECT SESSIONTIMEZONE, DBTIMEZONE FROM dual;

15. Can I set the session time zone to UTC?

• Yes, you can set the session time zone to UTC (Coordinated Universal Time) by using the 'UTC' time zone name or the +00:00 offset:

ALTER SESSION SET TIME_ZONE = 'UTC';

-- or

ALTER SESSION SET TIME_ZONE = '+00:00';

16. What is the default session time zone?

• If you do not explicitly set the session time zone, it will default to the database's time zone (i.e., the value returned by DBTIMEZONE).